Recombination of DNA is essential for maintaining genetic diversity as well as for repairing double-strand DNA breaks, The interaction between Rad51, the eukaryotic recombinase, and replication protein A (RPA), the eukaryotic ssDNA-binding protein, appears to be fundamentally linked to the efficiency of recombination. The interaction will be characterized biophysically and structurally by a variety of methods, including affinity chromatography, fluorescence, and NMR spectroscopy. The structural interface will be defined, elucidating the mode of interaction and providing insight into the mechanism by which Rad51 displaces RPA from ssDNA. Docking of the RPA and Rad51 structures will reveal the first known protein complex of RPA and will provide a basis for future experiments probing the structural and dynamic properties of higher order complexes. Additionally, analysis of this early step of the recombination process will increase our understanding of the molecular basis for progression through the multiple stages of DNA processing reactions. [unreadable] [unreadable] [unreadable] [unreadable]